Two cycle engine scavenging control



Oct. 5; 1943. "H. a; CAMNER ,855

IWO ems ENGINE S GAvLENGJNG GQMROE FilecLFgb. ,e, 1941 SCAl/ENGING A/RT0 ENG/NE ENGINE DRIVEN 4 GOVERNOR SCAVE/VG/NG AIR Nab T0 ENG/NE I-EN6/NE DRIVEN 4, w GOVERNOR J Patented on. 5, 1943 TWO CYCLE ENGINESCAVENGIN G CONTROL Hilding Gunnar Camner, Ektorp, near Stockholm,Sweden, assignor to Aktiebolaget Atlas Diesel, Stockholm, Sweden, acorporation of Sweden {Application February 6, 1941, Serial No. 377,636In Sweden March 13, 1939 4 Claims. (Cl. 123-65) In two-stroke-cycleinternal combustion motors having a centrifugal compressor orcentrifugal fan as a scavenging pump, some operating dimculties are metwith continuous operation at idling speed or at full speed with lowload. These dliliculties, for which the characteristics of thescavenging fan are partly responsible, have been obviated through thepresent invention, while the fuel consumption of the motor under suchoperating conditions has also been reduced by the invention.

When a two-stroke motor is running at a constant speed, the pressure inthe scavenging air receiver varies in a certain relation with the loaddepending on the pressure prevailing in the working cylinder, when theexhaust and scavenging ports are opened. Thus the scavenging pressure islower at idling speed or low load running than when under full load.

In motors fitted with positive cavenging pumps, these variations in thescavenging pressure do not cause any great inconveniences inasmuch assuch scavenging pumps deliver an approximately constant quantity ofscavenging air,

' independently of th back pressure against which they are operating. Inscavenging fans, on the other hand, a decrease in the scavengingpressure results in an increase in the quantity of air delivered by thescavenging fan, and this increase of the air quantity becomesconsiderable if the pressure characteristic of the scavenging fan isvery flat, which is desirable for other reasons.

Because of the increased quantity of scavenging air at idling speed andat low load, the motor will be greatly cooled .down, partly on accountof the smaller quantity of fuel consumed and partly ,by reason of theincreased quantity of scavenging air supplied by the fan. In additionhereto the fuel consumption of the motor increase by reason of theincreased power demand of the scavenging fan.

According to the present invention, which relates to such controllingmeans intended for twostroke-cycle internal combustion motors having acontrollable throttle member arranged either in the conduit between thefan and the motor cylinders, or on the suction side of the fan, or inboth of these places at the same time, said difliculties have beenobviated, whil improved operatlng properties of the motor have also beenobtained. The characteristic feature of the invention substantiallyresides in the throttle member being adapted to be controlledautomatically from the governor of the fuel pump or from some othercontrolling or regulating member which is indicative of the torque ofthe motor.

Preferab1y,the throttle member is arranged in the suction conduit of thescavenging fan, inasmuch as the best efiiciency of the scavenging fanwill be obtained thereby, while at the same time it is avoided that thescavenging fanwill operate under the pumping limit.

However, throttling of the suction conduit brings about a vacuum on thesuction side of the scavenging fan, whereby inconveniences withincreased axial pressures from the fan wheel and drawing in oflubricating oil may result. In such cases it will then be foundadvantageous to place throttle members both in the suction conduit andin the pressure conduit.

Preferably, the control may take, place from the governor of the fuelpump, either directly through motion transmitting members, or by meansof a servo-motor which is actuated by the pressure of the scavengingair, or by some other The invention is illustrated by way of afewexamples of embodiment in the accompanying drawing, wherein Fig. 1 isa diagrammatic representation of a throttling means on the suction sideof the fan, which is controlled automatically by the governor of themotor through a servomotor, while Fig. 2 shows an embodiment Where thecontrol of the throttle member takes place through a direct connectionbetween the controlling means of the fuel pump and the operating meansof the throttle member.

In Fig. 1, 24 designates the suctionpipe of the scavenging fan 23 and 2a throttle member built into the same in the form of a damper which maybe adjusted to different positions to control the passage area of thepipe 24. The damper is arranged on a shaft 3 which is connected by meansof a lever 4 with the piston rod 5 of a piston 6 which is movable withina cylinder 1 of a servo-motor. One side of the piston communicatesthrough a pipe 8 with a conduit for supplying pressure medium to thepiston. Ac-

cording to the drawing, the pressure medium consists of scavenging air,for which purpose the pipe 8 extends from the pressure conduit 25 of thescavenging fan, said latter conduit conveyso that the passage area willincrease or decrease successively at the movements of the piston. Whenthe piston H takes a position wherein the groove i3 registers' with theconduit 8, pressure medium. will be supplied to the'cylinder I, such prssure medium then acting upon the piston 6. In another position (thatshown by full lines in Fig. 1) the piston closes the conduit 8.

The piston H is connected to the governor iii of the motor by means of atwo-armed lever l5, pivoted as at M. Provided in the bottom of thecylinder 1 is a controllable opening I! of a comparatively small passagearea. I

The damper may also be arranged in the pressure conduit, as shown at 2,or, use may be made of one damper inthe suction conduit and anotherdamper in the pressure conduit.

The contrivance operates in the following manner: 2

When the motor is started, the damper 2 is kept approximatelycloseduntil the motor has been broughtup to its full speed. When theload on the motor diminishes or ceases, the deflection of the governorincreases, the lever'l5 being then turned into-the position shown bychain-dotted lines, so that the piston I I is moved into the bushing 9(toward the right in Fig. 1). A greater or smaller portion of the groovel3 will then come to register with the extension of the pipe 8, so

that pressure medium is supplied to the cylinder 1 of the servo-motorand forces the piston 6 toward the right in Fig. 1. By reason of theconical shape of the groove I3 in the control valve, the supply is thentaking lace successively. The damper 2 will then throttle the passagearea of the suction pipe to an extent corresponding to the decrease ofthe load, so that it will take the position shown by chain-dotted linesin Fig. l, for example. As long as the motor is being operated at lowload running or idling speed, the damper will be maintained in aposition where it throttles the passage through the air suction pipemore or less. When theload increases, the governor l8 will make asmaller deflection, which results in the lever l5 being turned into theposition shown by full lines in Fig. 1, such a movement being thentransmitted to 'the fuel injection pump through the connecting link i8that the fuel supply is increased. I The piston I1 is at the same timemoved toward the left in Fig. 1, so that the groove [3 is brought out ofregistry with the pipe 8 which latter is then throttled so that nopressure medium will be supplied to the cylinder I. The piston 6 is thenmoved back from the chain dotted to the full line position in Fig. 1under the influence of the spring 19. The pressure medium whichpreviously acted upon the piston 6 is then forced to escape through theaperture 11 in the bottom of the cylinder. The damper 2 is then openedand brought into a suitable position, for instance the position shown byfull lines in Fig. l. The position assumed is then determined by theratio between the area of the passage opening [3 and the area of theexit opening [1.

By suitably selecting the ratio between the size engine forautomatically controlling said throttle of the openings [3 and I! thethrottling may be caused to vary within the desired limits, for instancebetween a maximum of throttling at idling speed and a minimum ofthrottling at about half load running.

The invention also includes an arrangement whereby movement istransmitted directly from the governor of the motor to the damperwithout the use of the auxiliary members shown in Fig. 1.-

Fig. 2 shows an example of such an embodiment.

Here, the lever 4 of the damper 2 is connected by means of the rod 20 toa lever 2| actuated by the motor governor, said lever being pivoted atthe point 22 and having the link i8 extending to the fuel pump connectedthereto. In the con nection between .the lever 2| and the lever 4 thereare preferably arranged leverage members which are not shown in thedrawing, however.

This arrangement operates in an analogous manner to that shown in Fig.l, the full line positions corresponding to an increased load on themotor and the chain-dotted lines to a decreased load..

' The arrangementshown in Fig. 2 may obviously also be made use of inthe case that the lever 2| is operated manually, which, however, will befound to be inferior, since for the reasons stated hereinbefore theautomatic control offers great advantages.

In controlling the load and the speed of the motor from a distance, theshifting of the throttle member in the suction pipe or the pressure pipeof the fan may be effected by an electric or pneumatic remote controlmeans which may either actuate the controlling means of the fuel pump,the throttle member being then shifted automatically, or may actuate thethrottle member directly.

I claim:

1. In a two-stroke internal combustion engine having a fan for supplyingscavenging air and a throttle member for controlling the quantity ofscavenging air supplied by the fan, means responsive to variations inposition of a regulating member indicative of the torque developedby themember.

2.; In a two stroke internal combustion engine having a scavenging fanand a throttle member for controlling the quantity of scavenging airsupplied by the fan, a fuel injection pump, an engine driven governorfor controlling-said pump, ,a servo motor having an actuating member op-Jeratively connected to said throttle member,

.umeans for energizing said servo" motor to move said actuating memberand means automatically responsive to decrease in the torque developedby the engine below a predetermined value for.

operating said energizing means to cause said servo motor to move saidthrottle member toward closed position.

3. In a two-stroke internal combustion engine having a scavenging fanand a throttle member for controlling the quantity of scavenging airsupplied by the fan, a fuel injection pump, an engine driven governorfor controlling said pump, a servo motor having a cylinder and a pistonconnected to said throttle member to move the throttle member towardclosed position on admissionof pressure fluid to said cylinder, aconduit for supplying pressure fluid to said cylinder, a control valvelocated in said conduit for controlling admission of said fluid to saidcylinder 2,830,866 and means for automatically opening said valve whenthe torque developed by the engine falls below a predetermined value.

4. In a two-stroke internal combustion engine having a scavenging fanand a throttle member for controlling the quantity of scavenging airsupplied by the fan, a fuel injection pump, an engine driven governorfor controlling said pump, a servo motor having a cylinder and a pistonconnected to said throttle member to move the 10 throttle member towardclosed position on admission of pressure fluid to said cylinder, aconduit for supplying pressure fluid to said cylinder,

'9. control valve located in said conduit for controlling admission ofsaid fluid to said cylinder, said control valve havinga sliding controlmember provided with a conically shaped recess adapted to progressivelyopen or close the valve opening as said control member is moved in onedirection or the other, and means for automatically opening-said valvewhen the torque developed by the engine falls below a predeterminedvalue. 4

- HILDING GUNNAR CAMNER.

